The present invention relates generally to an apparatus and method for forming food products. More particularly, the present invention relates to an apparatus and method for forming generally flat, baked, farinaceous food products such as tortillas, taco shells, snacks and the like in a continuous fashion.
A wide variety of processes are known for forming dough intermediates into final products. Examples of such products include tortillas, pizza crusts, piecrusts, pastries, and cookies, as well as snack products, including chips or crisps and fruit snacks.
It is widely recognized that many aspects of the manufacturing processes can have a substantial impact on the price that a consumer pays for the product. Usually, the cost of a product decreases in proportion to an increase in the speed with which the product can be fabricated. Additionally, process improvements that simplify the associated equipment may lead to decreases in the costs of obtaining and operating such equipment.
In the manufacturing of flat products, such as tortillas, piecrusts, snack products, and the like, efforts have been increasingly directed toward reducing costs and increasing the speed of production. Traditionally, several manufacturing techniques have been utilized for economically and quickly forming tortillas on commercial production lines. A first popular method is known as die-cutting and a second popular method is known as pressing, both of which are described below.
In the die-cutting technique, dough is first formed in a commercial mixer. The dough is then transferred to an extruder that extrudes a sheet of dough onto a conveyor belt of a rolling and cutting machine to form a dough ribbon. In this step, the dough ribbon is gradually reduced to a predetermined thickness by sheeting and cross-rolling. Once the dough has reached a desired thickness, a die is actuated to cut the dough into the desired form. The formed dough products (or dough intermediates) are then separated from the remaining dough ribbon trim or “matrix” and are moved to an oven where they are cooked. The matrix is usually returned to the extruder for reprocessing.
Several problems and limitations exist with the die-cutting method described above. One such problem is that the remaining matrix is often mixed with one or more particular ingredients. For example, the dough ribbon is often coated with topical flour or starch prior to cutting to prevent the die from sticking to the dough. When this dough and flour is reprocessed, the extra flour and floor time can produce undesirable properties within the dough. For example, the topical flour can inhibit re-mixing, causing the subsequently processed dough product (e.g. tortilla) to be substantially inflexible or brittle, and can produce an undesirable taste in the product. In addition, having the dough products produced by this method usually imparts a rheoligical bias in the direction of sheeting to the resultant product. That is, the tortilla (or other resultant product) will crack when folded in the direction that is transverse or perpendicular to the direction of the sheeting. Moreover, the sheeting process described above does nothing to seal the surface of the dough. Sealing the surface of the dough traps leavening gasses during baking, which has been found to improve final bake quality of the product.
As mentioned above, a second common process for forming tortillas (or other dough-based, flatten products) is by pressing, which is also referred to as a hot press method. In practice, dough intermediate balls are formed, proofed, and fed onto a conveyor that carries several dough balls at a time into position between heated platens (up to 232° C. (450° F.)) of a tortilla press. Such relatively high temperatures must be imparted to the dough balls by the platens to overcome the inherent elastic tendency of the dough to snap-back after pressing. In other words, without sufficiently heating the dough, the pressed dough will typically thicken and shrink in size, snapping-back to a much smaller size. In addition, dough properties can vary from batch to batch, and may also vary significantly within a single batch. This creates further problems in providing a consistent and uniform product from a consumer standpoint.
In the pressing process, a batch of dough intermediate balls is transferred by a conveyer to a position between heated press platens. The conveyor is then stopped and the press is closed, compressing the balls into circularly shaped tortilla intermediates (or other food product) that are then transferred into an oven for baking. To this end, the press operation is characterized as including a compression period (during which the platens are driven to a desired spacing) followed by a holding period (during which the platens are maintained at the desired spacing). Using this method, the tortillas may be formed at reasonable production speeds; however, the time required for opening and closing the press and indexing the belt carrying the dough severely limits production to about 14 to 16 press strokes per minute. Generally, the press is the rate limiting step of a continuous production line. Further, the accepted technique of “proofing” the dough balls prior to pressing can significantly increase overall press processing time. In general terms, proofing entails placing the formed dough balls in a temperature and humidity controlled environment (typically 32° C. (90° F.), 70% relative humidity) for a period of time on the order of 5-15 minutes. It is believed that this processing step is essential to relax the gluten structure inherent to the dough intermediate balls, thereby lessening potential snap-back. Though viewed as being a press process requirement and reducing compression force output requirements of the pressing itself, proofing undoubtedly increases production time.
In addition to limited production speeds, the pressing method suffers from other drawbacks. For example, the individual components are more expensive as compared to machinery associated with the die-cutting technique. Moreover, the intermittent, reciprocating movement and engagement of the platens adds further complexity to the system. Additionally, alignment of the dough intermediate balls with the press platens increases the difficulty in operating the equipment and may contribute to other problems, such as misalignment which can lead to the tortillas (or other resultant food product) being irregular (e.g., not perfectly circular) or having a non-uniform thickness, such that they are not of an acceptable quality.
What is needed therefore is an apparatus and method that overcomes the difficulties set forth above and which can process flat, baked food products in an efficient manner while maintaining consistently good, quality products.